Aromatic polyimide, polyester and polyamide separation membranes

ABSTRACT

Gas separation membranes are made from aromatic polyimides, polyesters and polyamides in which the repeating unit of the main polymer chain A. HAS AT LEAST ONE RIGID DIVALENT SUBUNIT, THE TWO MAIN CHAIN SINGLE BONDS EXTENDING FROM WHICH ARE NOT COLINEAR, B. IS STERICALLY UNABLE TO ROTATE 360* AROUND AT LEAST ONE OF THESE BONDS, AND C. HAS 50% OR MORE OF ITS MAIN CHAIN ATOMS AS MEMBERS OF AROMATIC RINGS.

United States Patent 1 1 1111 3,899,309

Hoehn et al. Aug. 12, 1975 [5 AROMATXC POLYIMIDE, POLYESTER AND 3.567.632 3/1971 Richter et 111. 210/321 x POLYAMIDE SEPARATION MEMBRANES 3.686.] 16 8/1972 RIO 210/500 X 3.744.642 7/1973 Scala 61 al. 210/500 [75] lnventors: Harvey Herbert Hoehn. Hockessin.

Deli; John W. Richter, Kennett Square 1 Primary Ii.\'ur11i11er-Frank A. Spear, Jr.

[73] Assignee: E. I. du Pont de Nemours & (10..

Wilmington, Del.

[22] Filed: Jan. ll, 1973 1211 Appl. No.: 322.800

Related US. Application Data [63] Continuation-impart of Ser. No. 273.802. July 20.

1972. abandoned.

[ 5 7 ABSTRACT Gas separation membranes are made from aromatic polyimides, polyesters and polyamides in which the repeating unit of the main polymer chain a. has at least one rigid divalent subunit. the two [521 US. Cl. 29/16; 55/158; 210/23;

210/500 mam cham single bonds extending from which are 1511 Int. c1 BOld 53/22; BOld 31/00 9 l 0 [581 Field of Search 210/500. 490 507 321, b. is sterically unable to rotate 360 around at least 210/23; 55/16. I58; 23/2585; 264/41. 49; 204/296 one of these I c. has 50% or more of its main cham atoms as [561 References Cited members of aromatic rings.

UNITED STATES PATENTS 3,228,877 1/1966 Mahon 210/22 29 Claims, 1 Drawing Figure 1\ \\\\m 1 1 ll AROMATIC POLYIMIDE, POLYESTER AND POLYAMIDE SEPARATION MEMBRANES RELATED APPLICATION This application is a continuatiOnin-part of our application Ser. No. 273,802 filed July 20, 1972, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention concerns semipermeable membranes prepared from a class of polymers whose molecular morphology renders them highly useful in chemical separations.

2. Prior Art The use of polymeric materials as semipermeable membranes is well known. It is recognized that the chemical constitution of a polymeric material may largely determine its utility in this field and the search for polymers of superior utility continues. In U.S. Pat. No. 3,172,741, Jolley has shown the polymers such as polyacrylonitrile, polyethyleneterephthalate and hexamethyleneadipamide have utility as separation membranes and he points to certain structural characteristics of these polymers which contribute to this utility. In US. Pat. No. 3,567,632 Richter and I-Ioehn disclose permselective membranes from selected polyamides, polyacyl hydrazides, polysemicarbazides and polyureas. Neither of the patents disclose or suggest the polymeric membranes of this invention.

STATEMENT OF THE INVENTION The present invention is a gas separation membrane of which at least 50% by weight consists essentially of a polymer whose main chain has a repeating unit containing at least one group selected from the group consisting of aromatic imide, aromatic ester and aromatic amide in which said repeating unit a. contains at least one rigid divalent subunit, the two main chain single bonds extending from which are not colinear,

b. is sterically unable to rotate 360 around one or more of said main chain single bonds, and

c. more than 50% of the atoms in the main chain are members of aromatic rings.

These criteria define predominantly aromatic polymers whose molecules are unable to pack densely because of having within the repeating unit of the polymer chain at least one main chain single bond which makes an angle with at least one next adjacent main chain single bond and around which the polymer molecule is sterically unable to rotate freely. While it is not intended to be bound by speculation, it is considered that configurations as defined above render polymer molecules containing them incapable of packing as densely together as polymer molecules without such configurations, Specifically, the bend in the polymer chain caused by the noted angle cannot be accommodated in packing by free rotation around the bond. The structure of the solid polymer is thus kept permanently more open" to the passage of small gas molecules, resulting in higher flux rates for the passage of such gases.

The polyimides from which membrane materials of this invention are selected may be represented generally as polymers in which the repeating unit is as shown in formula I:

wherein R and R are, respectively, divalent and tetravalent organic radicals, i.e., with their bonds stemming from carbon atoms. These are illustrated in more detail below.

The polyesters from which the membrane materials of this invention are selected may be represented generally as polymers in which the repeating unit is as shown in formula II:

wherein R and R are defined as above and R is hydrogen, lower alkyl, or phenyl. These are illustrated in more detail below. The term lower in the specification and claims means 1-6 carbons.

The particular polyimides, polyesters and polyamides useful as membranes in this invention are selected on the basis of the three criteria noted above. Requirement (a) specifies that the repeating unit of the polymer contain at least one rigid divalent subunit, the two main chain bonds from which are not colinear. The rigid submits in a polymer chain are those atoms, groups of atoms, or cyclic structures which are joined to other units in the main chain by single bonds between two atoms. The single bond junction points in a polymer main chain are readily recognized from the structural formula of the polymer repeating unit and these points are the demarkation points between rigid subunits. Such a subunit is rigid because the angle between the two single bonds extending from the subunit is fixed. The two bonds from a rigid subunit are colinear (L) if they form an angle of about I", (particularly l7()l80) or if they are parallel and offset not more than 2A. Otherwise, they are noncolinear (N). Preferred polymers have 2-10 main-chain rigid subunits in the polymer repeating unit.

Requirement (b) specifies that the polymer chain contain at least one bond between rigid subunits around which bond the polymer chain is sterically prevented from rotating 360. This determination is based on the well-known textbook rules of stereochemistry. These rules are strictly incorporated into the design of the Corey-Pauling-Koltun Models (CPK Models) described by W. L. Koltun in Biopolymers 3, 665679 1965) and which are available from the Ealing Corporation, 2225 Massachusetts Avenue, Cambridge. Massachusetts, 02140.

A practical determination of whether a polymer satis fies requirements (a) and (b) is made as follows:

1. Draw the conventional two-dimensional representation of the polymer repeating unit and indicate the single bonds in the main polymer chain which separate rigid subunits.

2. For each rigid subunit indicate whether the two main chain bonds stemming from it are colinear (L) or non-colinear (N).

3. Construct the CPK Model of the polymer unit and from the model determine which of the bonds indicated in (l) are restricted from rotating through 360. Persons skilled in the field of stereochemistry would, of course, not need the model to make this determination. Illustrations of the above steps and the one which follows appear in the examples below.

The determination of requirement (c) that over 50% of the atoms forming the backbone chain of the repeating unit of the polymer be in aromatic groups can readily be made from the two-dimensional representation of the polymer repeating unit noted above. The 1 main chain atoms which are counted are those in the single atom and cyclic rigid subunits. In cyclic subunits in which the two single bonds stem from different atoms, all member atoms in the basic ring of the subunit are counted, e.g., p-phenylene counts 6 atoms. Side chain atoms such as hydrogen, carbonyl oxygen, alkyl groups, haloalkyl groups, carboxyl groups, ester groups, halogen substituents and other pendant groups are not counted. If both single bonds from a cyclic rigid subunit stem from the same atom, only that one atom is counted, e.g., 1,1-cyclohexylene counts 1 atom, the remaining pentamethylene being a pendant group. Aromatic rings include not only the hydrocarbon aromatic rings such as benzene, naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, indene, and the like, but also those heterocyclic rings commonly acknowledged to have aromatic character such as furan, benzofuran, dibenzofuran, thiophene, pyrazole, indole, benzimidazole, pyrazine, carbazole, pyri- 'dine, quinoline, acridine, imidazole, isoimidazole, and the like. See, for example, R. C. Fuson, Advanced Organic Chemistry," John Wiley & Sons, Inc., 1950, Chap. XXIV, Aromatic Character."

In the examples showing the determination of the above criteria, the single bonds separating rigid subunits are marked by drawing dotted lines across the two-dimensional representation of the polymer repeat ing unit and are identified by the letters A, B, C, D, etc. The rigid subunits are numbered 1, 2, 3, 4, etc. The rigid subunits are then tabulated along with a notation for each whether its two main chain single bonds are colinear (L) or non-colinear (N) and a notation as to which, if any, of these bonds are restricted from rotating 360. The proportion of the main chain atoms in the repeating unit which are in aromatic structures is also shown.

The invention also contemplates the use of copolyimides, copolyesters and copolyamides in which the respective repeating units of the copolymer members individually satisfy criteria (a), (b), and (c), as well as physical blends of two or more of these materials meet ing these criteria and also copolyimides, copolyesters, copolyamides and blends in which one or more members meet these criteria, those members constituting 50% or more of the membrane by weight.

The membranes of this invention may be prepared by any of the known means for forming organic polymers. Membranes in film form may be prepared by melt pressing, melt extrusion, solution casting, and the like. Membranes in tubular or hollow form may be prepared by melt spinning and wet or dry spinning from solution.

When the membranes of this invention are formed from polymer solutions in organic solvents, it may be desirable to incorporate up to lOO% by weight of soluble salt, based on the polymer, Le, a salt which is soluble (and preferably highly dissociated) in the polymer solution to the extent present and which is essentially chemically inert toward the polymer and the solvent. Suitable salts include LiCl, LiBr, LiNO CaCl etc.

In the membranes of this invention, there may be incorporated up to 50% by weight of the total composition of a compatible plasticizer of the type illustrated by the phthalateesters such as dibutyl, dicyclohexyl, dioctyl and diphenyl phthalates, the aryl sulfonamides such as the N-(lower alkyl)benzenesulfonamides and N-(lower alkyl)toluenesulfonamides, the organic phosphates such as triphenyl and tricresyl phosphate, the adipates such as dioctyl adipate and diisodecyl adipate and similar compatible esters. In solution preparations, the plasticizer may be incorporated by dissolving it in the polymer solution prior to casting or spinning. Plasticizers may also be incorporated by hot blending on mixing rolls or in an extruder prior to the formation of the membrane.

In a preferred embodiment of this invention, a polymer which satisfies requirements (a), (b) and (c) is dissolved at about 20% concentration in an anhydrous organic solvent. The solution is filtered to remove solids and is freed of dissolved gases. At a temperature in the rangefrom room temperature up to 150C. the solution is cast in film form on a support or spun through a cored spinneret to give a hollow fiber. The solvent is then removed. For exampleif a uniform membrane is desired, the solvent is evaporated preferably by heating about to 1 10C. On the other hand if an asymmetric membrane is desired, the film or fiber structure is quenched in a liquid which is a nonsolvent for the poly-* mer and a solvent for the organic solvent and additives already present. Preferably the quench liquid is water and the organic solvent is water-miscible.

Apparatus suitable for separation of gases, as removal of hydrogen from a mixture of hydrogen and methane, by a membrane in film form is shown in the FIGURE. In this FIGURE base section 11 and upper section 12 of permeation cell 10 are machined from corrosion-resistant metal. Film 13, the separation membrane, is a disk mounted against a porous support disk 14. When upper section 12 of the cell is bolted to lower section II, synthetic elastomer O-rings 15 seat firmly around the periphery of the membrane and against the metal. Inlet 16 for feeding gases into the cell is near the membrane. By-pass of a portion of the feed gas is provided through exit 17. Gas passed through membrane 13 is collected through a metal frit 18 into exit pipe 19. Pipe 19 is connected to a metal gas receiver (not shown) which is fitted with pressure measuring devices.

Some of the terms used to describe the performance of the membranes of this invention are defined as follows:

Selectivity The selectivity of a membrane in separating a twocomponent fluid mixture is defined as the ratio of the rate of passage of the more readily passed component to the rate of passage of the less readily passed component. Selectivity may be obtained directly by contacting a membrane with a known mixture of gases and analyzing the permeate. Alternatively, a first approximation of the selectivity is obtained by setting up the ratio of the rates of passage of the two components determined separately on the same membrane. Rates may be expressed as GTR or as 08 units.

Gas Transmission Rate (GTR) One characterization of membrane permeability used in this disclosure is the gas transmission rate. GTR data represent the steady state rate of gas transmission through a membrane. GTR values are not normalized for membrane thickness. For homogeneous membranes the GTR is inversely proportional to the sample thickness. When the thickness of the active part of the Volume area time X pressure GTR= The units selected for volume, area, time, and pressure are cm (STP), 100 in', 24 hours, and atmosphere, re- 40 spectively. Substituting these units in (1) gives (2):

GTR

Except in special cases, all measurements of transmitted gas as cm (STP) were made at 30C. GTR values were usually measured at gas pressures of 39.7, 114.7, 314.7, 614.7 and 1014.7 psia.

Centibarrer Permeation Coefficient (CE) The standard unit for the permeability coefficient in observing the permeability of polymer films to gases is defined as the barrier which is equal to in which cm (STP) is the volume of permeated gas at standard temperature and pressure,

cm is the thickness of the film,

cm is the area of film,

sec is the time, and

cmHg is the pressure.

(ASTM Test D 1434-66, 1970 Edition, Part 27, pgs 447 and 453 In the present application permeabilities are reported in centibarrers (08), a unit which is 1/ of the barrer as defined above. Centibarrer values can be calculated from the relationship:

c8 GTR X film thickness in mils X 0.6.

As stated previously, the polymers used in this invention are characterized by having the three elements (a), (b) and (c). As long as these are present in the polymer, R, R and R may be any divalent organic radical and R may be any tetravalent organic radical. It is to be noted it is possible to prepare polymers where all the Rs are derived from compounds shown in the various tables below but would still not have elements (a), (b) and (0). Such polymeric materials are not within the scope of the invention, but may be used in combination with the polymers of this invention in amounts up to 50% by weight.

The examples give various illustrations of the radicals which are used. Without any intent of limitation the radicals may be further illustrated as follows:

In formulas I, II and Ill, the divalent radicals R, R and R may be substituted or unsubstituted phenylene, naphthylene, biphenylene, anthrylene or where R is alkylene (including alkylidene) of up to 18 carbon atoms, aralkylene of up to l8 carbon atoms, haloalkylene (including haloalkylidene) of up to l8 carbon atoms in which the halogen(s) are fluorine, chlorine, bromine or iodine, oxygen, sulfur, SO

in which R and R are lower alkyl or phenyl. Preferred embodiments of R are alkylidene, haloalkylidene, aralkylidene, oxy and iminocarbonyl (NHCO). Preferred alkylene and haloalkylene moieties in R are those of 1-3 carbon atoms.

The tetravalent radical R may be a substituted or unsubstituted grouping:

am IZL as m where R is defined as above.

Substituents on the above divalent and tetravalent radicals, i.e., replacements for hydrogen in aromatic CH groups, may be alkyl of up to 18 carbon atoms such as methyl, ethyl, isopropyl, butyl, tert.-buty1, hexyl, and octadecyl, phenyl, halogen such as fluorine, chlorine, bromine and iodine, lower alkoxy, carboxyl, lower alkoxycarbonyl, carbacyl of up to 6 carbon atoms such as acetyl and hexanoyl, sulfo and sulfo salt of an alkali or alkaline earth metal. Preferred embodiments of R, R, R and R are those in which the aromatic portions are of the benzene or naphthalene series.

Additional dianhydride radicals are listed in Table 1. Suitable polyimides for use in this invention can be obtained when equivalent amounts of the dianhydrides shown in Table l are substituted, for example, for pyromelletic dianhydride in the procedure of Example l3, Part A.

Additional diamines are listed in Table II. Suitable polyimides can be obtained when equivalent amounts of the diamines shown in Table II are substituted, for example, for l,5diaminonaphthalene in the procedure of Example 15, Part A.

Polyesters suitable for use in this invention are obtained when, as in the procedure of Example l, Part A, 4,4-diphenylbis( trifluoromethyl)methane dicarboxylic acid dichloride is substituted for example for isophthaloyl chloride and the diols shown in Table lll are substituted for example for 2,2-bis(3,5-dichloro-4-hydroxyphenyl )pro'pane.

Additional suitable polyesters are obtained when equivalent amounts of the diacid chlorides of the dicarboxylic acids shown in Table IV are substituted, for ex ample, for isophthaloyl chloride in the procedure of Example l, Part A.

Additional suitable polyamides are obtained when equivalent amounts of the diamines shown in Table ll are substituted for 4-isopropylmetaphenylenediamine in the procedure of Example 31, Part A, and when equivalent amounts of the diacid chlorides of the dicarboxylic acids shown in Table IV are substituted for isophthaloyl chloride in the procedure of Example 3 l Part A.

A preferred group of polyesters and polyamides are copolyesters and copolyamides formed by reacting a glycol or a diamine with an equivalent amount of a mixture of isophthaloyl and terephthaloyl chlorides where the molar and weight proportions of the acid chlorides may vary from 99/1 to 1/99 respectively. Particularly preferred are copolyesters and copolyamides in which isophthaloyl chloride is used in excess of terephthaloyl chloride, especially where the ratio is 70/30.

TABLE I Dianhydrides l Pyromellitic dianhydridc 2. 3,4.3.4'-Diphenylsulfonetetracarboxylic dianhydn'dc 3. 3.4.3'.4'-Bcnzophenonctctracarboxylic dianhydridc 4. Pyrazinctctracarboxylic dianhydride 5. 3.4.3'.4-Diphcnyldimcthylmcthanctctrucarhoxylic dian hyd ride dian hydride 7. 2,3,6,7-Naphthalenetctracarboxylic dian hyd ridc 3. 4-Diphcnyltctracurboxylic diunhydridc TABLE II Continued 25. Calcium sulfometaphenylencdiamine 26. 4,6-Dichlorometaphenylene diamine 27. 2,4.6-Tfichlorometaphenylenediamine 28. 4.4'-Diaminotriphenylmethane 29. Bis(4-amino-2.5-dicthoxyphenyl) phenylmcthanc 30. 4-Isopropylmewphenylcnediaminc 3 l 2.5.2'.5 '-Tclrachlorohenzidine 32. 2.6-Dichloro-p-phcnylenediamine 33. 3.3'-Dichlorobcnzidinc 34. 2.2-Diamin(xliphcnylmcthanc 35. 2.2'-Diamino-3,5.6-trichlorodiphcnylmclhane 50 cc c1 cl oc rl oc u TABLE [I Continued Diamine 36. 2 2-Bis(4-uminophenyl )-1 3- diphcnylpropanc 20 and 30 of Table II.

TABLE III Diols cooqou-Auro- 4,4'-Dihydroxydiphenyl ether 4.4 '-Dihydroxydiphenyl sulfonc 4 .4 '-Dihyd roxydiphenylbis( trifluoromethyl )methane Lithium 2.4-dihydroxybenzenesulfonatc Resorcinol Hydroquinonc 2.2-Bis(4.4-dihydroxydiphenyl )propane 2.4-Dihydroxytoluene 4.4'-Dihydroxydiphenylmethane 4.4'-Dihydroxydiphenyl sulfide 2.6-Dihydroxypyridinc Bis(4hydr0xyphenyl )diethylsilane Bis(4-hydroxyphenyl )diphenylsilane 4.4'-Dihydr0xybiphenyl 4.4 '-Dihyd roxy-3.3 '-dimethoxybiphenyl Bis( 4-hydroxyphenyl )ethylphosphine oxide Bis( 4-hydroxyphenyl )butylamine Bis(4-hydroxyphenyl)methylaminc I .5'Dihydroxynaphthalene 4.4 '-Dihydroxy-3 .3 'dimethylbiphenyl N-( 3-Hydroxyphenyl )-4-hydroxybcnzamide 4-Hydroxyphcnyl 3-hydroxybenzoate N .N-Bis( 4-hydroxyphenyl )aniline 2.2-Bis( 3-chloro-4-hydroxyphenyl )propane 2.2-Bis( 3 .5dibrom-4-hydroxyphcnyl )propane Bis(4-hydroxyphenyl )isononylmcthane 2.2-Bis( 3.5-diisopropyl-4-hydroxyphenyl )decanc 2 2-Bis(4-hydroxyphcny1)isopentanc 4 4-Bis(3.5-dichloro-4-hydroxyphcnyl )heptane 2.2-Bis(3 5-dibromo-4hydroxypheny1)decane Bis( 3.5-dibromo-4-hydroxyphenyl )ether Bis( 3-chl0ro-5-methyl-4-hydr0xyphenyl )cther 3.3'-Dielhyl-4,4'-dihydroxydiphenyl 3 .5 .3 .5 '-Tetrahromo-4 4 '-dihydroxydiphcnyl Bis( 3.S-dibromo-4-hydroxyphcnyl )sulfone Bis( 3 .S-diisopropyl-4-hydroxyphcnyl )sulfone l .4-Dihydroxy-2.3-dichlorobcnzcnc I .4-Dihydroxy-2-brom03-propylbcnzcne 2.3-Bis( p-hydroxyphenyl )pcntane 2.2-Bis( 3-methyl5-t-butyl4-hydroxyphenyl )propanc 2 .2-Bis( 4-hydrnxyphenyl )-3-cyclohcxylpropanc 2.4-Bis( phydroxyphcnyl )heptanc 2.2-Bis( 3-cyclohcxyl-4-hydroxyphcnyl )propane Bis( 3-t-Butyl-4-hydroxyphcnyl )sulfonc 2.2-Bis( 3phenyl-4'hydroxyphcnyl )propanc I.1-Bis(4-hydroxyphenyl)-5-phcnylpcntanc Bis( Z-hydroxyphcnyl )methunc 2.2'-Dihydroxy-3.5.fi-trichlorodiphenylmcthanc 2.2-Bis(4-hydroxyphenyl)-1,3-diphcnylpropanc 2.2-Bis( 3.5-dichloro-4-hydroxyphcnyl )hexufluoropropanc Preferred diols are items l-3, 5-10, 19, 24, 25, 31 and 50 of Table III.

TABLE IV Dicarboxylic Acids Diphenyl ether 4.4'-dicarboxylic acid Diphenyl sulfone 4.4'-dicarboxylic acid Diphenylbis(trifluoromethyl)methane-4.4'-dicarboxylic acid Isophthalic acid Terephthalic acid 4.4'-Propylidenedibenzoic acid 4Methylisophthalic acid 4,4'-Methylenedibenzoic acid Diphenyl sulfide 4.4'-dicarboxylic acid 10 2,6-Pyridinedicarboxylic acid 1 I 4.4'-Diethylsilanedibenzoic acid 12 4.4'-Diphenylsilanedibenzoic acid 13 4,4' Bisbenzoi'c acid 14 4.4'-Bimnisic acid 15 Bis(4'carboxyphenyl)ethylphosphine oxide 16 1.5-Naphthalenedicarb0xylic acid 17 4.4-Bis(o-toluic) acid 18 4-Bromoisophthalic acid Preferred dicarboxylic acidsare items 1-6, 13 and 16 of Table IV.

SPECIFIC EMBODIMENTS OF THE INVENTION In the illustrative examples which follow, parts and percentages are by weight'unless otherwise specified.

EXAMPLE 1 Part A Polyester from isophthaloyl chloride and 2.2-bis( 3.5- dichloro-4-hydroxyphenyl)propane.

A mixture of 183 g of 2,2-bis(3.5-dichloro-4-hydroxyphenyl)propane, 1 liter of s-tetrachloroethane, 0.72 g

CH3 I Rigid Subunit Colinearity Restricted Bonds a N 3 L D 4 N D 5 N 6 N 7 N 8 N A The repeating unit has 2 L and 6 N rigid subunits, 2 bonds with restricted rotation, 2 of the N subunits have at least one bond with restricted rotation, and 18/23 (78%) of the atoms in the chain are aromatic. This polymer thus satisfies the requirements set out above.

Part B The polyester of Part A was dissolved in tetrachloroethane in an amount to give a 16% solution. The solution was filtered through a 5.0g. silver membrane. The filtrate was degassed to remove bubbles. The filtrate was cast on a glass plate which had been coated with a low molecular weight polytetrafluoroethylene wax dispersion (Vydax) and heated to l 10C. A 15 mil doctor knife was used to spread the solution. The film was then covered to protect the solution or the partially dried tacky film from dust. The cover was equipped with vents. After allowing the film to dry for 5 minutes at 1 10C vents in the cover were opened and the film was allowed to dry another 10 minutes. The 1.5 mil film was then stripped from the glass plate and tested as a permeation membrane for a mixture of oxygen and nitrogen using the apparatus of the Figure. The film permeated at 140 GTR and 126 cB. The film permeated nitrogen at 25 GTR and 22 C8. The selectivity, Sg WaS EXAMPLE 2 The procedure of Example 1, Part B was repeated using a 15 mil doctor knife. The film was covered and dried at 100C. for minutes after which vents were opened and drying continued for minutes. The clear, bluish, smooth, crisp, 2.4 mil film was stripped from the plate and tested for oxygen and nitrogen permeability. The film permeated 0 at 1 GTR and 166 C8 and N at 21 GTR and 30 CE. The was 5.5.

EXAMPLE 3 The procedure of Example 1, Part B was repeated, using a 10 mil knife in place of the 15 mil knife and under otherwise similar conditions except that the plate w s allowed to cool at room temperature for 15 min bel-. stripping the film. A film of 1.35 mil thickness was obtained. It permeated O at 22l GTR and 179 C8 and N at 40 GTR and 32 CE. S was 5.5.

EXAMPLE 4 The procedure of Example 1, Part B, was repeated four times with the exception that casting and drying temperatures of 50, 55, 60 and 70C were used respectively in place of l 10C.

The 1.5 mil film prepared at 50C permeated H at 1774 GTR and 1597 cB and CH at 58 GTR and 52 08. The S,, was 31.

The 1.45 mil film prepared at 55C permeated H at 1815 GTR and 1579 c8 and CH at 68 GTR and 59 c8. The SHZKH was 27.

The 1.5 mil film prepared at 60C permeated H at 1683 GTR and 1515 cB and CH at 63 GTR and 57 08. The S was 27.

The 1.5 mil film prepared at 70C permeated H at 1795 GTR and 1616 cB and CH at 64 GTR and 58 08. The SHKH was 28.

EXAMPLE 5 The Example of Exampale 1, Part A, 8 g, and 3.2 g of a mixture of N-ethyl-orthoand -paratoluenesulfonamides (Santicizer 8, Monsanto Co.) were'dissolved in 72 g tetrachloroethane. The solution was filtered through a 0.45 1. silver membrane, degassed, and cast on a Vydax -coated glass plate at 60C with a 15 mil knife. The film was covered and dried for 5 minutes with the vents closed and 10 minutes with the vents open. The film was allowed to cool and stripped from the glass plate. The 1.2 mil film permeated H at 569 GTR and 410 c3, and CH at 18 GTR and 13 cB. The SHK'4 was 32.

EXAMPLE 6 Part A The polyamide from m-phenylenediamine and a 70/30 mixture of isophthalic and terephthalic acid chlorides was prepared using the procedure shown by Richter and Hoehn in U.S. Pat. No. 3,567,632, col. 28, line 61 to col. 29, line 12. This polyamide is referred to as MPD-l/T (-70/30).

Part B This example concerns a semipermeable membrane made from a blend of a polyester which satisfies requirements (a), (b), and (c) with a polyamide. A casting solution was prepared using 10 parts of a solution containing 15 wt MPD-l/T (100-70/30) in tetrahydrofuran, 10 parts of a solution containing 15 wt of the polyester of Example 1, Part A, in dimethylacetamide, and 1.2 parts Santicizer 8. This solution was cast on a Vydax coated glass plate at room temperature with a 15 mil knife. The film was dried for 15 min at C. The 1.55 mil film permeated H at 572 GTR and 532 CE, and CH at 6 GTR and 6 CE. The Snum was 95.

EXAMPLE 7 Part A Polyamide from metaphenylenediamine and isophthaloyl chloride.

Under nitrogen a solution of 2.36 moles of metaphenylenediamine in 32 moles of N,N- dimethylacetamide was stirred and cooled at l0 to 0C and 2.36 moles of molten isophthaloyl chloride was added in small portions. During the addition the temperature was allowed to rise to 20C. The reaction was completed by heating the resulting viscous solution to about 50C. The solution was diluted to 9% polyamide by adding dimethylacetamide. The polymer was isolated from this solution by drowning in crushed ice and ice water under vigorous agitation. The polymer was recovered by filtration, washed with water and dried under vacuum at 80C.

Part B A solution of 3 g of the polyester of Example 1, Part A, in 17 g. of tetrahydrofuran was mixed with a solution of 3 g polymetaphenylene isophthalamide (prepared as The repeating unit has 6 N and 2 L subunits, 4 bonds with restricted rotation, 3 of the N subunits have at least one bond with restricted rotation, and 18/23 of the chain atoms are aromatic.

in Part A) in 17 g of dimethylacetamide. 5 Pan B The combined solution was filtered through a 0.81.1. silver membrane. The filtrate was cast on a Vyclax A Solunon was Prepared from g of the pfflyester coated glass plate at room temperature in a dust-free of Part A and g of chlProform' The Soluuon was cabinet with a 15 mil doctor knife. The film was alfiltered through a Sllver membrane degassed lowed to y for 1 5 min at room temperature in the 10 and cast on a Vydax coated glass plate at room temperdust free Cabina and was the transferred to a hot ature in a dust-free cabinet using a mil doctor knife. plate maintained at 1 10C and allowed to dry for 5 min. The film was auowed to dry mmutes at room The film was stripped, air dried and then dried in a temperature Stnpped and dned m a Vacuum at i temperature. The crystal-clear, smooth, crisp, 1.8 mi :55? ggg ig g zg 3523 3 23 3 32??? 15 film permeated H at 5687 GTR and 6142 c8 and CH,

2 4 and 77 CB. The was 61 at 126 GTR and 136 C13. The SHKH4 was 45.

EXAMPLE 8 C The procedure of Example 6, Part B was repeated exh solunon describe? m Part B was added i p that the p ticizer (Santicizer 8) was omitted The cient diethylphthalate to give an amount of plasticizer 2 mil film containing polyamide and polyester in the eqilal to 40% by weight based on the polymer' This so ratio 50/50 permeated H2 at 867 GTR and 1040 CB and lution was then cast on a Vydax coated glass plate at CH at 13 GTR and I 6 CE The S was 67 room temperature in a dust-free cabinet with a 15 mil 4 doctor knife. The film was allowed to dry at room tem- EXAMPLE 9 25 perature in a dust-free cabinet for 15 minutes, stripped P rt A and dried in a vacuum at room temperature. The crysa tal-clear, smooth, soft, 1.9 mil film permeated 1-1 at Polyester from isophthaloyl Chloride and 1886 GTR and 2150 0B and CH at 338 GTR and 385 dichloro-4-hydroxyphenyl)hexafluoropropane. B. Th was 5 6 The procedure of Example 1, Part A was repeated except that the 2,2-bis(3,5-dichloro-4-hydroxyphenyl) propane was replaced by a chemically equivalent amount of 2,2-bis(3,5-dichloro-4-hydroxyphenyl)hexa- EXAMPLE )0 fluoropropane. The polymer was isolated as before. P A The polyester prepared as above was checked against an re uirements (a), (b) and (c) as follows: Polyester from a 1:1 mixture of iso hthaloyl chloride Ill 13 E Ii G H A c 1 I c I o l 0 l l l I n l n I O C C O l I l l I l l 1C]. 1 I I l 1 l l 5 6 7 I 5 I Rigid Subunit Colinearity Restricted Bonds and terephthaloyl chloride and 2,2-bis( 4- l L A B hydroxyphenyl)hexafluoropropane. 2 N ig The procedure of Example 9, Part A was repeated 3 L C. D except that half of the isophthaloyl chloride was re- 2 S B placed with terephthaloyl chloride. The polymer was 6 N isolated as before. 2 g X The polyester prepared as above was checked aganist requirements (a), (b) and (c) as follows:

A B C D F G H I 1 cF I o 10! C O C 5-0 1 l -O-C -o- 1 l l l J I l J 1 3 6 Rigid Restricted Subunit Colincurity Bonds 1 L B 2 N B. C 3 L C 4 N 5 N 6 N (l) L (T) 7 N 8 N The repeating unit (1) has 2 L and 6 N subunits. The repeating unit (T) has 3 L and 5 N subunits. In both (1) and (T) there are 2 restricted bonds and one of the N subunits has two bonds with restricted rotation. In both (1) and (T) 18/23 of the chain atoms are aromatic.

Part B A solution prepared from 6 g of the polyester shown in Part A and 34 g of chloroform was filtered through a 0.45 p. silver membrane, degassed and cast on a Vydax coated glass plate using a 15 mil doctor knife at room temperature in a dust-free box. The film was allowed to dry for 15 min at room temperature and was then stripped. The clear, 1.6 mil film permeated H at 2627 GTR and 2522 cB and CH at 70 GTR and 67 c8. The S was EXAMPLE 1 l A solution prepared from 6 g of the polyester of Example 10, Part A and 54 g of tetrachloroethane was filtered through a 0.45;. silver membrane and degassed. The solution was cast on Vydax coated glass plate at 100C using a 25 mil doctor knife, covered and dried for 5 min. The vents in the cover were then opened and drying continued for 10 min. The clear, crisp,- 1.7 mil film obtained on stripping permeated H at 2071 GTR and 2112 cB and CH at 52 GTR and 53 0B. The SHK-H4 was EXAMPLE 12 The procedure of Example 1 l was repeated except that a mil knife was used in place of a mil knife. The smooth, clear 1.0 mil film permeated H at 2772 GTR and 1663 cB and CH. at 92 GTR and 55 c8. The s py was EXAMPLE 13 Part A Polyimide from pyromellitic dianhydride and 4- isopropyl- 1 ,3-diaminobenzene.

To a solution of 15 g of 4-isopropyl-l,3- diaminobenzene in 190 ml of dry N,N- dimethylacetamide under nitrogen was added with stirring 21.8 g of pyromellitic dianhydride, rinsed in with an additional 68 m1 of dimethylacetamide. After minutes of stirring 30.63 g of acetic anhydride and 30.36 g of triethylamine were added. The resulting solution was stirred 1 hour at room temperature and then 1 hour at 50C. The polyimide was precipitated by drowning in excess methanol under vigorous agitation, recovered by filtration, washed with methanol and dried under vacuum.

The polyimide prepared as shown above was checked against requirements (a). (b) and (c) as follows:

A B O A E l l l h N l l c C 1 I -1"? 1| 1;

J CH. 0 0 l Rigid Restricted Subunit Colinearity Bonds 1 N A 2 L A The repeating unit has 1 L and l N subunit, one bond with restricted rotation and 12/18 chain atoms are aromatic.

Part B A solution of 3 g of the polyimide of Part A in 17 g of dimethylacetamide was filtered through a 0.45 p. silver membrane, degassed, and cast on a Vydax coated glass plate at 100C with a 15 mil doctor knife. The film was covered and allowed to dry for 5 min after which the vents in the cover were opened and drying was continued for 10 min. The clear, brown, 0.75 mil film obtained on stripping permeated hydrogen at 24,263 GTR and 10,918 cB and CH at 977 GTR and 440 0B. The S was 25.

EXAMPLE 14 Part A A solution of 15 g of the polyimide of Example 13, Part A, 0.75 g of lithium nitrate and g of dimethylacetamide was filtered through 0.45; silver membrane, degassed, and cast on an lnconel plate at l 10C with a 15 mil knife and dried for 5 min. The lnconel plate was then taken from the hot plate directly into a bath of methanol, cooled to 0C, and allowed to remain there for 30 min. The 1.05 mil film was stripped from the plate and allowed to air dry. The film permeated H at 46,664 GTR and CH at 2,662 GTR. The SHWH was 18.

Part B.

EXAMPLE 15 Part A 3,4,3 ,4 '-diphenylhexafluoroiso- 1,5-

Polyimide from propylidene tetracarboxylic dianhydride and diaminonaphthalene.

To a solution of 31.64 g of 1,5-diaminonaphthalene in 350 m1 of N,N-dimethylacetamide under nitrogen was added 88.87 g of 3,4,3',4'-diphenylhexafluoroisopropylidene tetracarboxylic dianhydride. The mixture was heated to 69C and stirred for 1 hour. Then a mixture of 82 g of acetic anhydride and 82 g of triethylamide was added in small portions over a period of about minutes, starting with the solution at 53C. Within a few minutes of stirring a peak temperature of 605C was reached. Stirring continued for one hour as the temperature gradually dropped. The resulting solution was drowned in a large excess of methanol under vigorous agitation. The precipitated polyimide was reunder vacuum, first at room temperature for about 16 hours and then for 3 hours at 260C.

. The polyimide prepared as shown above was checked against requirements (a), (b) and (c) as follows:

The repeating unit contains 4 N subunits, 4 bonds with restricted rotation, all of the N subunits have at least one bond having restricted rotation, and 22/29 of the chain atoms are aromatic.

Part B A solution of g of the polyimide of Part A in 80 g of dimethylacetamide was filtered through a 0.8 p. silver membrane, degassed, cast on a Vydax coated glass plate at 100C using a 25 mil doctor knife. The film was covered, dried at 100C. for 5 min. with the cover vents closed and 10 min. with the vents open. The film was then stripped. The clear 2.67 mil film permeated H at 2912 GTR and 4,665 cB and CH at 75 GTR and 120 0B. The SHWH was 39.

EXAMPLE 1 6 Part A Polyimide from 3,4,3,4-diphenylhexafluoroisopropylidene tetracarboxylic dianhydride and 4,4- diaminodiphenyl ether.

To a solution of 40.05 g of 4,4-diaminodipheny1 ether in 350 ml of dry pyridine under nitrogen at 50C was added 88.87 g of 3,4,3,4-dipheny1hexafluoroisopropylidene tetracarboxylic dianhydride. The tempera ture rose to a peak of 74C within a few minutes. After 1 hour of stirring 82 g of acetic anhydride was added. The temperature rose to a peak of 66C within a few minutes. Stirring was continued for 3 hours, during the latter portion of which the solution was heated to 100C. After cooling the solution to room temperature the polyamide was precipitated by drowning in a large excess of methanol under vigorous agitation, recovered by filtration, washed with methanol and dried under vacuum, first for 4 hours at 170C and then for 3 hours at 260C.

The polyimide prepared as shown above was checked against requirements (a), (b) and (c) as follows:

l n 1 1 s l 1 L l 3 I E F A 1?" 8 1 C C a. l

u N I C l l 1 g I 5 6 sfib u it Colinearity Restricted Bonds B N i h E 5 N E.F 6 N F The repeating unit has 4 N and 2 L subunits, 2 bonds with restricted rotation, 3 of the N subunits have at least one bond with restricted rotation, 24/32 of the atoms in the chain are aromatic.

Part B A solution of 30 g of the polyamide of Part A and 170 g of dichloromethane was filtered through a 0.45 p. silver membrane, degassed and cast on a Vydax coated Inconel sheet at room temperature in a dust-free cabinet with a 15 mil doctor knife. The solution was dried for 15 min and the film stripped. The clear, yellow film, 1.42 mils thick, permeated H at 3197 GTR and 2724 013 and CH at 106 GTR and CE. The SHWH was 30.

EXAMPLE 17 A solution of 20 g of the polyimide of Example 16, Part A in 80 g of dimethylacetamide was filtered through a 0.841. silver membrane, degassed, and cast on a Vydax coated glass plate at C with a 25 mil doctor knife. The film was covered, dried at 100C for 5 min after which the vents on the cover were opened and drying continued 10 min. The clear, crisp 2.60 mil film permeated H at 1378 GTR and 2150 cB and CH at and CB. The SH2 pu was 29.

EXAMPLE 18 PartA Polyimide from 3,4,3',4'-diphenylhexafluoroisopropylidene tetracarboxylic dianhydride and 4- isopropyl-l ,3-diaminobenzene.

To a solution of 31.21 g of 4-isopropyl-l ,3- diaminobenzene in 350 ml of dry pyridine under nitrogen at 50C was added with stirring 92.29 g of 3,4,3 ,4- diphenylhexafluoroisopropylidene tetracarboxylic di anhydride, rinsed in with an added 50 ml of pyridine. Within a few minutes the temperature rose to a peak of 76C. After stirring for about 2 hours the temperature was 52C and 85.2 g of acetic anhydride was added. Within a few minutes the temperature rose to a peak of 66C. After one hour of stirring the solution was heated to 99C and stirred for about 20 minutes. The polyimide was precipitated from the cooled solution by drowning it in a large excess of methanol under vigorous agitation. The polyimide was recovered by filtration, washed 3 times with methanol and dried under vacuum, first for 4 hours at 100C and then for 4 hours at 260C.

The polyimide prepared as shown above was checked against requirements (a), (b) and (c) as follows:

A c n l J l c c': l I

Restricted Rigid Bonds Subunit Colincarity C. D D, A'

The repeating unit has 4 N subunits, 3 restricted bonds, all of the N subunits have at least one bond with restricted rotation, 18/25 of the chain atoms are aromatic.

Part B A solution of 85 g of the polyimide of Part A in 340 g of dimethylacetamide was filtered through a 0.45 s

silver membrane, degassed and cast on a Vydax coated glass plate at 100C using a mil doctor knife. The film was covered and allowed to dry for 5 min after which the vents in the cover were opened and film allowed to dry another 10 min. The 1.79 mil film permeated H at 11,150 GTR and 11,975 cB and CH at 851 CvTR and 914 cB. The 5 was 13.

EXAMPLE 19 Part A an hour. With the solution at 45C a mixture of 82 g of triethylamine and 82 g of acetic anhydride was stirred in. Within 10 minutes, the temperature rose to a peak of 52C and then began to drop. Stirring was continued for about 2 hours. The resulting polyimide solution in dimethylacetamide was concentrated to 32% by evaporation, diluted to 10% by adding 359 g additional dimethylacetamide and then concentrated to about 15% polyimide by evaporation and used without further treatment.

The polyimide prepared as shown above was checked against requirements (a), (b) and (c) as follows:

Repeating unit has 4 N subunits, 2 bonds with restricted rotation, 3 of the N subunits have at least one bond with restricted rotation, and 18/25 of the atoms in the chain are aromatic.

Part B The 15% solution of the polyimide in dimethylacetamide from Part A was filtered, degassed, and cast on a Vydax coated glass plate at 100C. with a 25 mil doctor knife. The film was covered and allowed to dry for 5 minutes at 100C. The vents in the cover were then opened and drying was continued for 10 minutes. The clear, crisp 1.61 mil film permeated H at 3054 GTR and 2950 cB and CH at GTR and 68 0B. The 5H2 [CH4 W215 EXAMPLE 20 Part A Polyimide from 3,4,3',4'-diphenylhexafluoroisopropylidene tetracarboxylic dianhydride and paraphenylenediamine.

To a solution of 21.63 g of paraphenylenediamine in 350 ml of N,N-dimethylacetamide at 50C. under nitrogen was added with stirring 8887 g of 3,4,3',4'- diphenylhexafluoroisopropylidene tetracarboxylic dianhydride, rinsed in with an additional 25 ml of dimethylacetamide. Within 5 minutes the temperature rose to a peak of 77C. Stirring was continued for about 1 hour, at which time 82 g of triethylamine and 82 g of acetic anhydride were added. Stirring was continued for about 2 hours. The polyimide was precipitated by drowning the solution in a large excess of methanol under vigorous agitation. The polyimide was recovered by filtration, washed twice with methanol and dried under vacuum, first for 16 hours at room temperature and then for 3 hours at 260C.

The polyimide prepared as shown above was checked against requirements (a), (b) and (c) as follows:

rinsed in with an added 25 ml of dimethylacetamide. Within a few minutes the temperature peaked at 765C and began to drop. After stirring for about 1 A C I A hour 41 g of triethylamine and 41 g of acetic anhydride I 7, 3 were added. The temperature soon peaked at 66C and i be an to drop. After stirring for 2 hours, the polyimide C l C l C g l I I was precipitated by drowning the solution in excess N CF5 N methanol under vigorous agitation. The polyimide was I I recovered by filtration, washed twice with methanol E l l E and dried under vacuum, first for about 18 hours at t I O 0 room temperature and then for 3 hours at 260C.

I The polyimide prepared as shown above was checked I l l 2 3 1 a ainst re uirements (a), (b) and (c) as follows:

I. .1.- C D r? i" G 11 O I J O A 1 1 I g I i l u l t 0 0 I l I u i I I I cv I I C 1%! T '6? N i l C 5 C i I I l i 1 I I l I l O I O I 1 l l I 1 7 5 19 10 1 Rigid Restricted 3O Rigid Subunit Colinearity Bonds Subunit Colinearity Restricted Bonds 1 L 1 N 2 N C 2 N 3 N C, D 3 N 4 N D 4 N 5 N 6 N 7 N 8 N I 9 N 1, J Repeating unit has 1 L and 3 N subunits, 2 restricted N J bonds, all of the N subunits have at least one bond with restricted rotation, and 18/25 of the atoms in the chain are aromatic.

Part B EXAMPLE 21 Rart A Polyimide from 3,4,3,4'-diphenylhexafluoroisopropylidene tetracarboxylic dianhydride and the bisamide from metaphenylenediamine and metaaminobenzoic acid.

To a solution of 34.64 g of N,N'-metaphenylenebis(m-aminobenzamide) in 175 ml of dry N,N-dimethylacetamide under nitrogen at C was added with stirring 44.44 g of 3,4,3',4-diphenylhexa fluoroisopropylidene tetracarboxylic dianhydride,

The repeating unit has 10 N subunits, 2 bonds with restricted rotation, 3 of the N subunits have at least one bond with restricted rotation, and 30/41 of the atoms in the chain are aromatic.

Part B A solution of 12 g of the polyimide of Part A in 68 g of dimethylacetamide was filtered through 0.45 p. silver membrane, degassed, and cast on a Vydax coated glass plate at C. with a 25 mil doctor knife. The film was covered and dried for 5 min. The vents in the cover were then opened and drying continued for 10 min. The clear, smooth, crisp 1.62 mil film permeated H at 1268 GTR and 1232 c8 and CH at 24 GTR and 23 0B. The S was 53.

EXAMPLE 22 A solution of 9 g of the polyester of Example 9, Part A, and 51 g of dimethylacetamide was filtered through a 045p. silver membrane, degassed and cast on a Vydax coated glass plate at 100C. with a 25 mil doctor knife. The film was covered, dried at 100C. for 5 min. with the cover vents closed, and for 10 minutes with the cover vents open. The film was stripped and tested without further treatment. The clear, crisp 1.7 mil film permeated oxygen at 922 GTR and 940 CE and nitro gen at 106 GTR and 108 0B. The SOzHz was 8.7

EXAMPLE 23 Part A Part B To 20 g of the polyimide solution from Part A was added 0.17 g ethylene glycol. The solution obtained Polyimide from 3,4,3,4-diphenylhexafluoroisopropylidene tetracarboxylic dianhydride and wasodega sse d and cast on a Vydax coated glass plate at diaminobenzoic acid 100 C with a 25 mtl doctor knife. The film was cov- To a solution of 15.22 g of 3,5-diaminobenzoic acid cred dned for 5 mmfiafter which vents m cover in 175 ml of dry NNdimethYlacetamide under mm} were opened and dry ng was continued for minutes. gen at was added with Stirring 4444 g of343,,4 The clear, smooth, crisp, 1.31 mil film permeated H at -diphenylhexafluoroisopropylidene tetracarboxylic di- 10 2684 GTR and 21 10 CB and CH4 at 29 GTR and 23 anhydride, rinsed in with an added 25 ml of dimethyl- The 2 m was acetamide. Within 2 minutes the temperature peaked EXAMPLE 24 at 745C and began to drop. After about l hour of stir- P A ring, 82 g of triethylamine and 82 g of acetic anhydride art were added. Within 14 minutes the temperature Polyimide from 3,4,3,4'-diphenylhexafluoroisopeaked at 56C and began to drop. After stirring for 2 propylidene tetracarboxylic dianhydride and 3,3 hours the solution was concentrated to 25% polyimide diaminobenzanilide. in dim'ethylacetamide by evaporation under vacuum To a solution of 15.05 g of 3,3'-diaminobenzanilide first at C and then at C. It was then diluted to in ml of N,N-dimethylacetamide under nitrogen at 10% polyimide by adding 332 g of dimethylacetamide, 2 50C was added with stirring 29.68 g of 3,4,3',4'- followed by concentrating to 15% polyimide by evapodiphenylhexafluoroisopropylidene tetracarboxylic diration and filtering through a 0.45;. silver membrane. anhydride. Within a few minutes the temperature The polyimide prepared as shown above was checked peaked at 55C. After about an hour of stirring, 55 g 0t against requirements (a), (b) and (c) as follows: triethylamine and 55 g of acetic anhydride were added.

A A l l l Rigid After stirring for about an hour and a half the polysubum Cohmamy Rcsmcted Bmds imide was precipitated by drowning in a large excess 01 1 N 45 methanol under vigorous agitation. The polyimide was i recovered by filtration, washed twice with methano' 4 N b and dried under vacuum, first for about 16 hours at room temperature and then for 3 hours at 260C. A1 0.1% concentration in dimethylacetamide at 25C the The repeating unit has 4 N subunits, 2 bonds with re- 50 polyimide had an inherent viscosity of 1.15. stricted rotation, 3 of the N subunits have at least one The polyimide-amide prepared as shown above was bond with restricted rotation, and 18/27 of the atoms checked against requirements (a), (b) and (c) as folin the chain are aromatic. lows:

A ll L: I) E C F G A l I 1 I I u a 1 I I 9 i i C I 9 3 E C N N I I l l l I l l E l l J I O i l o J l 5 6 7 l 3 1 32 Rigid Restricted and casting on a Vydax coated glass plate at 100C with suhun cmmclmy Bmds a 25 mil doctor knife. The films were covered and dried l N for 5 min after which the vents on the cover were 2 N opened and drying was continued for 10 min. The films i 5 were then stripped from the plate and placed in a vac- 5 N F uum chamber and heat treated at 260C for 6 hrs under a vacuum of 2p" The films were then tested for permeation of hydrogen and methane as shown in Table V.

TABLE V Thickness H- Selectivity Mole (mils) Permeation Permeation Pi /CH 1.5-ND ODA GTR CB CIR CB Cast from 1054 solution The repeating unit has 7 N subunits, 2 bonds with re- EXAMPLE 26 stricted rotation, 3 of the N subunits have at least one part A bond with restricted rotation, and 24/33 of the atoms in the chain are aromatic.

Part B A solution of 15 g of the polyimide-amide of Part A in 85 g of dimethylacetamide was filtered through a 0.45;; silver membrane. degassed, and cast on a Vydax coated glass plate at 100C with a 25 mil doctor knife. The film was covered, dried for min, after which the vents in the cover were opened and drying was continued for minutes. The 1.56 mil film permeated H at 1328 GTR and 1243 cB and CH 'at 16 GTR and 0B. The SHWH4 was 83.

EXAMPLE 25 Part A A series of five polymers and copolymers were prepared, the first by repeating the procedure of Example 15, Part A. The second, third, fourth and fifth were prepared by the same procedure except that 25%, 50%, 75% and 100% respectively of the 1,5- diaminonaphthalene (1.5-ND) was replaced by a molecular equivalent amount of 4,4'-diaminodipheny1 ether (ODA).

Part B Films were prepared from the five polyimides of Part A by preparing 20% solutions in dimethylaeetamide A polyamide was prepared using the procedure of the Richter and Hoehn patent mentioned above as shown in Example 6, Part A, with the exception that 1 1.5 mole percent (20 weight percent) of the mphenylenediamine was replaced by a molecular equivalent amount of calcium sulfometaphenylenediamine of the formula H N NH SO Ca(1/2) to obtain the corresponding copolyamide, referred to as MPD/CaSMPD-l/T (88.5/l1.5 /30).

Part B Polyimide/polyamide blends were prepared by dissolving together in varying proportions the polyimide of Example 16, Part A and the polyamide of Part A above, the amounts of the two polymers being selected to give a total of 15% polymer weight in solution in dimethylacetamide. The resulting solutions were cast on Vydax coated glass at C using a 25 mil doctor knife. The films were first dried for 5 minutes at 100C with the cover vents closed and then for 10 minutes with the vents open. The films were tested for permeation of hydrogen and methane as shown in Table VI.

33 34 EXAMPLE 27 TABLE IX Polyimide/polyamide blends were prepared by dissolving together in varying proportions the polyimide C i of Example Part A and the polyamlde of Example 5 Thickness (mils) H2 Permeation Permeation Selectivity 26, Part A. Amounts of the two polymers were selected Knife Film GTR cB GTR cB H /C1-1 to give a total of polymer weight in solution in dimethylacetamide. The resulting solutions were cast on Vydax coated glass at 100C. using a 25 mil doctor 15 0.70 5213 2139 96 40 54 knife. The films were first dried for 5 minutes at 100C. 4423 2521 90 49 10 1.30 3680 2870 66 52 56 with the cover vents closed and then for 10 rnmutes L53 2736 2594 51 49 5 with the vents open. The films were then tested for per- :8 3-23 3: 31;; 3 2; 1; meation of hydrogen and methane as shown in Table VII.

TABLE VII Thickness CH, Selectivity Wt 71 in Blend (mils) Permeation Penneation H. .CH4 Polyimide Polyamidc cB GTR cB 50 1.39 1413 1178 48 40 29 75 25 1.43 2819 2419 100 86 28 20 1.47 3 I22 2754 I36 I20 23 15 1.311 3840 3180 139 115 28 10 1.44 4476 3867 195 I68 23 5 1.47 5224 4608 212 I87 25 0 2.71 3542 5759 144 235 25 EXAMPLE 28 EXAMPLE 30 The procedure of Example 19, Part B, was repeated Poly(4-isopropyl-m-phenylene) isophthalamide except that the doctor knife thickness was varied in Part A order to observe the effect of varying film thickness on the permeation of hydrogen and methane. Details of this study are shown in Table VIII.

TABLE VIII The procedure of Example 20 was repeated except that the doctor knife thickness was varied in order to observe the effect of varying film thickness on the permeation of hydrogen and methane. Details of this study are shown in Table IX.

A glass reactor equipped with a stirrer, reflux condenser and dropping funnels was flamed out under vacuum and purged with nitrogen. Into the reactor was placed 83.62 g (0.567 mole) of 4-isopropylmetaphenylenediamine (cumene diamine). Dimethylacetamide (884.2 g) was added in two portions with stirring and the resulting solution was cooled to about 0C. Isophthaloyl chloride (1 l6.75 g, 0.575 mole) was added in small portions over a period of 6 hours, the reaction temperature being held in the range of 41 to 52C. The reaction mixture was then drowned in ice and water with vigorous agitation. The precipitated polyamide was recovered by filtration and dried to constant weight. There was obtained I50 g of polyamide with inherent viscosity of 0.38. Inherent viscosities in this and the following Examples were measured at 0.1% weight/volume in dimethylacetamide at 25C.

The repeating unit of the polyamide prepared as shown above was checked against requirements (a), (b) and (c) as follows:

C D E F A I II I 0 I O 1 I I u I I n I 'N-TC I Cq- I 1 1 I I 1 1 I c11(c113)- 1 I 1 2 1 b 11 .5 I 6 I The repeating unit has six N subunits, one bond with restricted rotation, two of the N subunits have one bond with restricted rotation, and 12/16 of the main chain atoms are aromatic.

Part B Y A solution of 40 g of the polyamide from Part A in EXAMPLE 34 Poly( 4-isopropyl-m-phenylene) terephthalamide Part A Using the procedure of Example 30. Part A, a solution of 64.12 g (0.427 mole) of 4-isopropylmetaphenylenediamine in 678 g of dimethylacetamide was treated slowly with 86.65 g (0.427 mole) of terephthaloyl chloride during a period of 2.5 hours, kee ing the reaction temperature in the range of 35 to 55C. After the indicated recovery, there was obtained 111 g of polyamide of inherent viscosity 0.41.

The repeating unit of the polyamide prepared as above was checked against requirements (a), (b) and (c) as follows:

stripped film was dried overnight under vacuum at room temperature. The film was then immersed first in distilled water at room temperature for 1 hour and then in acetone for 1 hour, after which it was air-dried and further dried under vacuum at room temperature overnight. The l.46-mil film permeated H at 943 GTR and 826 CE and CH at 8 GTR and 7 C8. The SHZMM was A B C D E F A H l-i O I a I I l I l I g u l I u I i I i I I 1 I l I 1 i l Cl'l( CH 2 I i i 1 1 I 2 5 i 5 I 6 I I I 160 g of dimethylacetamide was filtered through a 0.45 Rigid Subunit Colinearity Restricted Bonds p. silver membrane, degassed and cast on a Vydax 1 N B coated glass plate at l 10C with a -mil doctor knife. 3 2 N B The film was covered and dried for 5 minutes at 1 10C 3 N with the cover vents closed and 10 minutes with the g s vents open. The film was stripped from the plate and 6 N air-dried. The 1.48-mil film permeated H at l 104 GTR and 980 c8 and CH at 19 GTR and l7 CE. The 5,, was 58 The repeating unit has five N and one L subunits, one bond with restricted rotation, two of the N subunits EXAMPLE 31 have one bond with restricted rotation and 12/16 of the The procedure of Example 30, Part B was repeated g st g atoms are aromanc' up to the stripping of the film from the plate. The 40 a stripped film was immersed in distilled water at room A solutfon of 15 g offhe polyamlde from Part A temperature for 20 hours and then in acetone for l 85 of dlmethylacemmde was filtered through a hour. The film was then air-dried. The 1.5l-mil film Silver membrane degoassefl and i on a vyqax rmeated H0 at 951 GTR and 862 CB and CH at 7 coated glass plate at l 10 C with a 15-.mrl doctor knife. g and 6 i The S was 136 4 45 The film was covered and dried for 5 minutes at l 10C y with the cover vents closed and 10 minutes with the EXAMPLE 32 vents open. The film was stripped from the plate'and The procedure of Example 30 Part B was repeated air-dried. The 1.25-mil film permeated H at l240 GTR up to the stripping of the film from the plate. The i CB and CH4 at 20 GTR and cB'The "2"'"4 stripped film was dried overnight under vacuum at as room temperature. It was then immersed in distilled water for 2 hours, air-dried, and further dried under EXAMPLE 35 vacuum overnight at room temperature. The 1.58-mi1 Poly( p pyl-mphenylene) film permeated H at 721 GTR and 684 c8 and CH at i p i e/ rephthalamide 7 GTR and 7 0B. The S was 103. Part A EXAMPLE 33 Using the procedure of Example 30, Part A; a solution of 47.37 g (0.315 mole) of 4-isopropylmeta- The Procedure of Example 30, Part B was repeated phenylenediamine in 501 g of dimethylacetamide was up to the stripping of the film from the plate. The

treated slowly with 64.12 g (0.315 mole) of a /30 mixture of isophthaloyl chloride/terephthaloyl chloride during a period of 5 hours, keeping the reaction temperature in the range of 45 to 50C. After the indi caied recovery, there was obtained 86 g of copolyamide of inherent viscosity 0.53.

The repeating unit of the copolyamide prepared as shown above was checked-against requirements (a), (b) and (c) as follows: 

1. THE PROCESS OF SEPARATING FLUIDS USING A SEMIPERMEABLE MEMBRANE OF WHICH AT LEAST 50% BY WEIGHT CONSISTS ESSENTIALLY OF A POLYMER WHOSE MAIN CHAIN HAS A REPEATING UNIT CONTAINING AT LEAST ONE GROUP SELECED FROM THE GROUP CONSISTING OF AROMATIC IMIDE, AROMATIC ESTER AND AROMATIC AMIDE GROUPS, IN WHICH SAID REPEATING UNIT A. CONTAINS AT LEAST ONE RIGID DIVALENT SUBUNIT, THE TWO MAIN CHAIN SINGLE BONDS EXTENDING FROM WHICH ARE NOT COLINEAR, B. IS STERICALLY UNABLE TO ROTATE 360* AROUND ONE OR MORE OF SAID MAIN CHAIN SINGLE BONDS, AND C. HAS MORE THAN 50% OF ITS MAIN CHAIN ATOMS IN AROMATIC GROUPS, THE SAID AROMATIC IMIDE REPEATING UNIT HAVING THE FORMULA -R-N<(-CO-)2>R''<(-CO-)2>NWHEREIN R AND R1 ARE, REPSECTIVELY, A DIVALENT AND TETRAVALENT ORGANIC RADICAL, THE SAID AROMATIC ESTER REPEATING UNIT HAVING THE FORMULA -R2-OOC-R3-COOWHEREIN EACH OF R2 AND R3, ALIKE OR DIFFERENT, IS A DIVALENT ORGANIC RADICAL, AND THE SAID AROMATIC AMIDE REPEATING UNIT HAVING THE FORMULA -R-N(-R7)-CO-R3-CO-N(-R7)WHEREIN R AND R3 ARE AS DEFINED ABOVE AND R7 IS HYDROGEN, LOWER ALKYL OR PHENYL.
 2. The process of separating fluids of claim 1 in which the polymer is a polyimide.
 3. The process of separating fluids of claim 2 in which the polymer is polypyromellitimide of 4-isopropyl-1,3-diaminobenzene.
 4. The process of separating fluids of claim 2 in which the polymer is poly(4,4''-(bis(trifluoromethyl)-methylene)dibenzene-1, 2,1'',2''-tetracarboxylic diimide) of 1,5-naphthylenediamine.
 5. The process of separating fluids in claim 2 in which the polymer is poly(4,4''-(bis(trifluoromethyl)-methylene)dibenzene-1, 2,1'',2''-tetracarboxylic diimide) of 4,4''-diaminodiphenyl ether.
 6. The process of separating fluids of claim 2 in which the polymer is poly(4,4''-(bis(trifluoromethyl)-methylene)dibenzene-1, 2,1''2''-tetracarboxylic diimide) of metaphenylenediamine.
 7. The process of separating fluids of claim 2 in which the polymer is poly(4,4''-(bis(trifluoromethyl)-methylene)dibenzene-1, 2,1'',2''-tetracarboxylic diimide) of paraphenylenediamine.
 8. The process of separating fluids of claim 1 in which the polymer is a polyester.
 9. The process of separating fluids of claim 8 in which the polymer is poly(4,4''-(ditrifluoromethyl-methylene)dibenzene-1,1''-diyl) isophthalate/terephthalate.
 10. The process of separating fluids of claim 8 in which the polymer is poly(4,4''-(ditrifluoromethylmethylene)di(2,6-dichlorobenzene)-1,1''-diyl) isophthalate/terephthalate.
 11. The process of separating fluids of claim 8 in which the polymer is poly(4,4''-(ditrifluoromethylmethylene)di(2,6-dibromobenzene)-1,1''-diyl) isophthalate/terephthalate.
 12. The process of separating fluids of claim 8 in which the polymer is poly(4,4''-(dimethylmethylene)di(2-chlorobenzene)-1,1''-diyl) isophthalate/terephthalate.
 13. The process of separating fluids of claim 8 in which the polymer is poly(4,4''(dimethylmethylene)di(2,6-dichlorobenzene)-1, 1''-diyl) isophthalate/terephthalate.
 14. The process of separating fluids of cLaim 1 in which the polymer is a polyamide.
 15. The process of separating fluids of claim 14 in which the polymer is poly(4,4''-(bis(trifluoromethyl)methylene)di-p-phenylene) isophthalamide/terephthalamide.
 16. The process of separating fluids of claim 14 in which the polymer is poly(4-isopropyl-m-phenylene) isophthalamide.
 17. The process of separating fluids of claim 14 in which the polymer is poly(2,5,2'',5''-tetrachlorobiphenylene) isophthalamide.
 18. The process of separating fluids of claim 14 in which the polymer is poly(1,5-naphthylene) isophthalamide/terephthalamide.
 19. The process of separating fluids of claim 14 in which the polymer is poly(4,6-dichloro-m-phenylene) isophthalamide/terephthalamide.
 20. The process of separating fluids of claim 14 in which the polymer is poly(2,6-dichloro-p-phenylene) isophthalamide/terephthalamide.
 21. The process of separating fluids of claim 14 in which the polymer is poly((3,3''-dichlorobiphenylene)/(m-phenylene)) isophthalamide.
 22. The process of separating fluids of claim 1 in which the fluid is a mixture of gases.
 23. The process of separating fluids of claim 22 in which the polymer is a polyimide.
 24. The process of separating fluids of claim 22 in which the polymer is a polyester.
 25. The process of separating fluids of claim 22 in which the polymer is a polyamide.
 26. A fluid-separation apparatus comprising: a fluid-permeation cell; a fluid inlet and a fluid outlet connected to said cell; and a semipermeable membrane dividing the cell between the inlet and the outlet; at least 50% by weight of said membrane consisting essentially of a polymer whose main chain has a repeating unit containing at least one group selected from the group consisting of aromatic imide, aromatic ester and aromatic amide groups, in which said repeating unit a. contains at least one rigid divalent subunit, the two main chain single bonds extending from which are not colinear, b. is sterically unable to rotate 360* around one or more of said main chain single bonds, and c. has more than 50% of its main chain atoms in aromatic groups, the said aromatic imide repeating unit having the formula
 27. The fluid-separation apparatus of claim 26 in which the polymer is a polyimide.
 28. The fluid-separation apparatus of claim 26 in which the polymer is a polyester.
 29. The fluid-separation apparatus of claim 26 in which the polymer is a polyamide. 